Method of making clutch pulley assembly

ABSTRACT

A clutch pulley assembly primarily designed for use with electromagnetic clutches for driving air conditioning compressors on automobiles and the like wherein the component parts of the clutch pulley assembly are fabricated from stampings with a reduction in the amount of machinery required to complete the device. The method of making and assembling the structure is part of the invention and includes the press forming of a web disc for supporting pulley grooves from sheet steel having desirable magnetic properties to produce an annular flange portion thereon at the outer edge thereof and extending substantially perpendicular thereto, then punching a central hub receiving aperture in the disc and then mounting the central aperture of said disc on a central hub made from a tube section. A die forming method of manufacturing a pulley groove is also disclosed. A section of steel tubing is cut to length, this section is press formed by axially moving dies, and then the pulley groove is completed by both axially and radially moving forming dies of multi-segment type. The pulley groove thus formed is then pressed upon the machined outer flange surface of the web disc in which magnetic flux blocking slots have also been punched.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.630,886, filed Nov. 11, 1975, for Clutch Pulley Assembly and Method ofMaking Same now U.S. Pat. No. 4,004,335, issued Jan. 25, 1977.

BACKGROUND OF THE INVENTION

This invention relates generally to an improved method of fabricatingelectric clutch pulley assemblies to reduce the cost of materials andlabor. Electric clutches with pulleys thereon are normally used fordriving air conditioner compressors in vehicles, such as automobiles,trucks, boats, airplanes, et.

DESCRIPTION OF THE PRIOR ART

In the past in constructing electromagnetic clutch pulleys forautomotive air conditioner compressors and the like, such structureshave been made from steel forgings requiring an extensive amount ofmachining in order to meet the critical dimensions as required for auseful product. The forgings themselves are relatively expensive, andthe cost of machining same even more so.

The known prior art pulley structures which are fabricated fromstampings, etc., are not normally designed to the critical size anddimensional limitations as are required by pulley structures to be usedwith electromagnetic clutches. These clutches in automotive airconditioner compressor applications and the like rotate at extremelyhigh speeds and require very close adherences to size tolerances.

Known prior art devices which may be pertinent to this invention arelisted as follows:

U.S. Pat. Nos. 2,074,199: Mar. 16, 1937; 2,095,025, Oct. 5, 1937;2,646,689, July 28, 1953; 2,787,914, Apr. 9, 1957; 2,846,893, Aug. 12,1958; 2,906,134, Sept. 29, 1959; 2,995,044, Aug. 8, 1961; 3,094,881,June 25, 1963; 3,722,309, Mar. 27, 1973.

None of these known prior art devices offers the new and unique featuresof the invention disclosed herein.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a new method offabricating an electric clutch pulley assembly to reduce cost ofmaterials and labor.

Another object of the present invention is to provide an improved methodof making a clutch pulley assembly which eliminates the high cost ofsteel forgings and provides a basic assembly for use with various sizesof die made pulley grooves, thus reducing manufacturing inventory andyet providing a large range of sizes available from stock.

Another object of this invention is to eliminate high priced forgingcomponents for an electric clutch pulley assembly and to use fabricatedcomponents from sheet steel and tubing for all the parts of saidassembly.

A further object of this invention is to provide an electric clutchpulley assembly fabricated from sheet steel and tubing which has thesame magnetic properties as a solid pulley machined from a solid castingor forging.

A still further object of this invention is to fabricate a clutch pulleyassembly having less weight than similar pulleys made from castings orforgings which is important in automobile and airplane applicationswhere weight is a problem.

A still further object of this invention is an improved method of makingand assembling the clutch pulley assembly to achieve the objectsaforesaid.

These and other objects are achieved according to the present inventionby fabricating the components of the electric clutch pulley assemblyfrom sheet steel and tubing, rather than making the components from asteel forging or casting, which necessarily requires extensive machiningin order to reach the desired dimensional characteristics as requiredfor this critical type application with an electric clutch.

Electric clutches for automotive and other vehicle air conditionercompressor use operate at very high rotational speeds so require thattheir size dimensions be quite exact. Also, the dynamic balancing ofsuch assemblies is important because of the high rotational speeds andbecause unbalance of any of the components will cause heavy vibrationwhich is or can be dangerous, or at the very least quite annoying.Reference is herein made to prior U.S. Pat. No. 3,842,378 issued Oct.15, 1974 to William L. Pierce and assigned to Pitts Industries, Inc.,wherein an electric clutch pulley assembly is fully disclosed andexplained. As disclosed in this patent, the present type of pulley ismade from a low carbon steel forging which is machined all over leavinglittle more than half its original weight. In this type of manufacture,even though highly automatic turning equipment is used, the large amountof machining is expensive and wasteful. Even the cost of tool inserts issignificant. The new way to manufacture this electric clutch pulleyassembly is as disclosed in this invention, and as disclosed in ourprior co-pending application Ser. No. 630,886, of which the inventiondisclosed herein is an improvement. As disclosed this inventioneliminates the high priced forging altogether by fabricating theassembly from tubing and sheet steel. It has been discovered that asubstantial weight reduction is achieved, a reduction in cost and timeis achieved, and the resulting structure has the same desirable magneticproperties of the solid pulley formerly used. This is important forproper performance as an electric clutch in the application set forthabove.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an end view of an electric clutch pulley assembly in reducedsize according to the present invention.

FIG. 2 is a cross sectional view taken generally along line 2--2 of FIG.1.

FIG. 3 is a plan view, reduced in size, of the hub, flange and web discas assembled according to this invention.

FIG. 4 is a cross sectional view taken generally along line 4--4 of FIG.3.

FIG. 5 is a perspective view of the web disc prior to forming and as cutfrom a blank of sheet steel having desirable magnetic properties.

FIG. 6 is a cross section through the center of the web disc of FIG. 5after the flange portion is formed on the outer circumference thereof.

FIG. 7 is a cross section of the web disc after the punching step forforming the large center aperture with flared edge.

FIG. 8 is a plan view of the web disc after forming by the method ofthis invention.

FIG. 9 is a perspective view of a section of steel tubing as provided inthe first step of the method of this invention for making a pulleygroove.

FIG. 10 is a side elevational view, partly in cross section, showing thenext step in the method of forming a pulley groove by this invention.

FIG. 11 is another elevational view, partly in cross section, showingthe final step in the method of forming a pulley groove by thisinvention.

FIG. 12 is a perspective view of the completed pulley groove as formedby the method of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings in detail, the clutch pulley assembly asmade by the method of the present invention is generally referred to inFIG. 2 by the reference numeral 10. This clutch pulley assembly isadapted to transmit power from a power source, such as a vehicle engine,to a vehicle accessory load, such as an air conditioner compressor, notshown. The power shaft 14 of the compressor accordingly extends into theclutch assembly and is provided with a tapered end portion 16 which isheld assembled to the hub by means of a bolt, not shown, threaded intothe shaft, 14. A key (not shown) is also provided in suitable keyways16' and 19 to lock hub 18 to shaft 14. Mounted on the hub 18 is abearing assembly 26 for rotationally supporting the drive pulleyassembly 30 which is the structure of this invention. The pulleyassembly 30 is adapted to be drivingly connected to the vehicle engineby a pulley belt, not shown, and the pulley assembly 30 forms part ofthe clutch mechanism 10 together with an armature assembly 20.

The pulley 30 is rotatably mounted on the hub 18 by the bearing assembly26 in fixed axially spaced relationship to the armature assembly 20 inorder to form an axial air gap 21 therebetween. The armature assemblyincludes a radially outer portion 38 that is displaceable axially intoengagement with a friction end face 44 on the pulley assembly 30 bymeans of an electromagnetic coil assembly 46 which is fixedly mounted bythe frame 48 bolted to the housing of a compressor. The coil assembly 46projects into an annular cavity 50 formed in the pulley assembly 30 andis of a conventional construction. The electromagnetic coil assembly isenergized in a manner well known by those skilled in the art wheneverthe vehicle engine is in operation and when so energized generates amagnetic field 92 that extends from its casing 51 made of materialhaving a low magnetic reluctance property. The pulley assembly 30 isalso made of material having low magnetic reluctance in order to permitthe establishment of magnetic fields therein. Also, the axiallydisplaceable portion 38 of the armature assembly is made of a materialhaving a low magnetic reluctance.

The displaceable portion 38 of the armature 20 is coupled to themounting flange portion 24 by means of a plurality of leaf springs 62pivotally connected at opposite ends by connector 64 to the radial outerportion of the mounting flange 24 on one axial side and by means ofpivot connectors 66 to the radially inner portion of the movable discportion 38 on the same axial side. The leaf spring elements 62 willtherefore yieldably resist axial movement of the movable disc portion 38into engagement with the pulley assembly 30 until such time aselectromagnets 46 are energized. For more details of this structure,reference is made to prior patent No. 3,842,278. Like reference numeralsare used herein to correspond with those in said patent.

The pulley assembly 30 has a flanged web portion 78 which hascircumferential slots 74 and 76 therein to magnetically separateradially inner and outer portions of this web portion of the pulleyassembly.

When the electromagnetic assembly is energized the magnetic fieldproduced thereby, which is characterized by the flux path 92 as shown inFIG. 2, extends through the material of the components of the pulleyassembly 30 and through the armature disc portion 38. Note, that asshown in FIG. 2, the disc portion 38 is shown separated (gap 21) fromthe friction surface 44 of the web flange portion 78 which is theposition when the flux is not present, i.e., electromagnets are notenergized. Obviously, once the electromagnets are energized and fluxpath 92 occurs, the armature disc 38 will be in firm frictional contactwith member 78 and friction surfaces 44 and gap 21 will not be present.

The new and improved method of making the clutch pulley assembly willnow be described. The flange web portion 78 (FIG. 4) of the overallpulley assembly 30 is formed from a disc of sheet steel of desirablemagnetic properties by means of a press and die arrangement.

FIGS. 5 through 8 illustrate the steps of the method of forming theflange web disc portion 78. As shown in FIG. 5, a basic disc ofappropriate size 178 is cut from a sheet of steel having the necessarymagnetic properties. A small central aperture 142 is normally alsopunched or drilled in the disc for centering and alignment purposes. Thedisc 178 is then press formed by appropriate die and press structure toprovide a flange portion 79. The present press and die arrangement issuch that a sharp corner 77 is generally left when the flange portion 79is formed from the basic disc member 178. This sharp corner 77 is latermachined off so that a greater friction face 44 will be exposed forcontact with clutch armature 38. After the flange portion 79 has beenformed from the disc 178 a large central aperture 52 is punched therein.This large aperture 52 normally is provided with a slight edge taper 53.The completed flange web disc (now labelled 78) is shown in FIG. 8 priorto assembly into the overall clutch hub assembly as shown in FIG. 4.

Looking at FIG. 4, the center hub 80 is made from long tubing which issliced or cut into appropriate short sections and then the inner surfaceof each section is machined to produce the recessed portion 81 and theabutment 82. Another recessed portion 85 with another abutment 83 isprovided on the same end as the recess 81 but on the outside of the tubehub 80. The web flange disc 78, 79, which has been formed as describedabove with reference to FIGS. 5 through 8, is then mounted on the tubehub 80 and die staked to the hub by die swaging all around the reducededge thereof as shown at 84. The flared edge 53 around the aperture 52aids in the forming of a proper joint. This has proven to be a verystrong and magnetically efficient joint. After the step of die swaging,the slots 74 and 76, that define the pole areas of the magnetic clutch,are punched out of the member 78. This punching step does cause a slightdistortion of the flange portion 79 and therefore a machining step ofthe outside diameter and inside diameter of the flange is required. Thisis indicated by the dotted line portions marked 86 and 88 on FIG. 4.This machining, of course, does not require the heavy machinerypreviously required for making the entire pulley structure from forging.Also, the sharp corner projection 77, if present from the formingoperation, may be removed by machining at this same time.

Once the outer surface of the flange member 79 has been machined to avery close tolerance, then pulley grooves, such as indicated byreference numeral 53 in FIGS. 2 and 12, are assembled thereon. Normally,the clutches have pulley grooves of six inch or seven inch diameter forapplication to various models of automobiles. One groove is normallyactually used, but two are generally provided to minimize stocking ofseveral models. A groove having a 60° belt receiving portion is muchused with foreign cars, while American automobiles generally use beltreceiving portions in the range of 36°. The hub and flange assembly ofFIGS. 3 and 4, as made by the method disclosed hereein, is useable withall of the pulley grooves of various sizes and dimensions. Thus, astandard hub assembly manufactured according to the method of thisinvention is useable with various different pulley grooves in order toreduce stock inventory and offer flexibility of total assembly.

The pulley groove 53 shown can be made by several methods of fabricatingsheet material, such as spinning, splitting, or rolling, which methodsare more fully described in our co-pending application Ser. No. 630,886.A preferred method of forming the pulley groove 53 will now be describedin detail with reference to FIGS. 9 through 11.

A short section of cylindrical steel material is cut from a length ofwelded or extruded steel tubing. This section 153 in FIG. 9 is ofsubstantially the correct internal diameter for use with the web discflange 79 of the basic clutch hub assembly. After the cutting of theshort section of tubing 153, the section is formed with a concavesurface around the periphery thereof by a second step of the method asindicated in FIG. 10. Round die members 160 are designed and constructedwith curved projecting portions 161 and mounted upon any conventionaltype axially movable press structure such as indicated in general byreference numerals 162 and 164. As can be visualized, when the tubesection 153 is placed between the dies 160 which are then pressedtogether, the tube section is shaped with the convex surface 153' asindicated in FIG. 10.

The third and final step of forming the pulley groove is accomplished byboth an axial and radial forming operation as shown in FIG. 11. Dies 170have an annular configuration to match that of the desired angle for thepulley groove, as indicated by surfaces 172, and with small axiallyprojecting portions 174 adjacent the points of abutment of therespective die members. The projections 174 on the mating surfaces ofthe dies 170 are designed so as to provide the desired width for theinner aperture 52 of the pulley flange 53. The dies 170 are mounted uponsimilar press structure 162' and 164' as for the step of FIG. 10. Inaddition to the annular dies 170, additional radial die structure 180 isprovided to simultaneously press inwardly against the axially formedpulley groove 153'. These die members 180 are also mounted upon movablepress members 182 similarly to those 162 and 162' already described. Themembers 180 may each be semi-circular in shape, or less, as necessaryfor a proper pressing operation. Upon completion of the third step asshown in FIG. 11, the final pulley groove 53 is produced. If necessary,a slight machining of the aperture 52 may be provided, though normallyin actual practice the accuracy of the die forming and pressingoperations are sufficient for the pulley groove to be accurately sized,including shoulder number 107 and ready to be press fitted upon themachined outer surface of flange 79 against locating shoulder 106without any additional machining of the pulley groove being necessary.Once the pulley groove 53 is pressed upon the flange 79 by press fittingas described above, it may be further staked or welded if desired tosecurely retain same as mounted.

As disclosed in our patent application, a combination grease retainerand bearing retainer 31 is also provided. This retainer 31 is normallyassembled when the bearing is pressed into the recessed inner portion 81of the hub 80. This retainer comprises an annular member having a largehole therein 32 and a recessed dipped flange portion 34 with the outeredge thereof making an angle of approximately 30° from the vertical. Asshown in FIG. 2, this retainer locks the bearing 26 in the hub 80 withinthe recessed portion 81 by means of a press fit and spring force actionof lip 34. It holds the bearing 26 against the shoulder 82 formed by therecess portion 81 and also acts to retain any grease that may purge fromthe seal from migrating to the friction surface 44. This is animprovement over former designs wherein a separate grease retainer cupis inserted, then the bearing, and finally the bearing retainer at theother end. FIG. 1 shows the electrical connecting wires 11 and 13 forthe electromagnet structure of the overall clutch assembly and thesupport plate 48 for attachment of the assembly to a compressor housing.The keyway 19 in the hub 18 is also clearly shown.

The disclosed structure and method of making an assembly thereof fromsheet steel and steel tubing having good magnetic properties produce aclutch pulley assembly for electromagnetic type clutch devices which isnew and unique to the field.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:
 1. A method of making a clutchpulley assembly for an electromagnetic clutch comprising the followingsteps:a. cutting a short section of tubing from a long piece of tubingto form the hub portion of said assembly, b. machining one end of saidshort section of tubing to have an undercut outer edge, c. press forminga disc of metal to have an outer flange extending substantiallyperpendicularly from the outer edge of said disc, d. punching anaperture in the center of said disc, e. mounting the aperture of saiddisc on the undercut edge of said tubing section, and f. die swaging theend of said tubing section so that the hub section and disc becomeintegral and make a good strong and magnetically efficient joint.
 2. Themethod as set forth in claim 1, together with the additional step ofpunching out annular slots in the disc for the purpose of providingbarriers to the flow of magnetic flux lines in said disc.
 3. The methodas set forth in claim 2, together with an additional step of machiningthe outer surface of the perpendicular extending flange to reduce theouter circumference thereof to a desired size for receiving accuratelysized pulley grooves thereon, and the further step of removing bymachining any projecting lip at the outer corner of the disc and flangeformed by the pressing step so that the surface of the disc will have agreater frictional contact area.
 4. The method as set forth in claim 3,further including the additional step of press fitting as least oneaccurately formed pulley groove on the outer machined flange surface. 5.The method of claim 4 including the further additional step of anchoringthe contact joint between the pulley groove and the hub flange member.6. The method as defined in claim 5, wherein step (a) includes theadditional step of undercutting the inner surface of the tube section bymachining to provide a proper dimensioned surface for reception of abearing therein and with an abutment to limit the position of thebearing.
 7. The method set forth in claim 3, together with theadditional step of forming a pulley groove by the process of dieforming, and the further step of press fitting the pulley groove overthe outer machined flange surface of the main hub assembly.
 8. Themethod set forth in claim 7, wherein the process of die forming thepulley groove includes cutting a short section of steel tubing,partially forming said short section of steel tubing into a concavecircumferential shape by axial press dies, and final shaping of saidpulley groove by a two part axial and radial die forming operation.
 9. Amethod of making a clutch pulley assembly for use in an electromagneticclutch comprising the steps of:a. cutting a short section of tubing froma long tube of steel having desirable magnetic properties, b. machiningsaid short section of tubing to have an undercut ridge on the outersurface of one end and an undercut inner suface extending from the sameend but stopping short of the other end to leave a bearing retainingridge within the inner surface of said tube, c. cutting a disc fromsheet steel having desirable magnetic properties, d. press forming saiddisc to produce an annular flange portion thereon at the outer edgethereof and extending substantially perpendicular thereto, e. punching acentral aperture in said disc, f. mounting the central aperture of saiddisc on the outer undercut edge of said tube section, and g. die swagingthe end of said tube section so that the tube section and disc areintegral to produce a good magnetically efficient joint.
 10. The methodas set forth in claim 9, together with the additional steps of (h)punching annular slots in said disc to form magnetic flux barriers, and(i) machining the inner and outer surfaces of the flange portionextending from said disc and the outer surface of said tube section soas to produce a hub assembly having the desired accurate dimensions. 11.The method as set forth in claim 10, together with the additional stepsof (j) fabricating a pulley groove from sheet steel, and (k) pressfitting said pulley groove upon the outer flange surface of said hubassembly.
 12. The method as defined in claim 11, wherein step (j)includes the additional steps of cutting a short section from a lengthof steel tubing, partially forming the short section with a concaveouter circumference by means of axial movable dies, and finally formingthe pulley groove by means of axial and radial forming dies.
 13. Themethod of claim 12, including the further additional step of die stakingthe pulley groove to the hub flange member.
 14. The method as defined inclaim 12, together with the additional step of undercutting the innersurface of the hub tube section by machining to provide a properdimensioned surface for reception of a bearing therein and with anabutment to limit the position of the bearing.